Electron discharge device



Y March 7, 1933. w HULL 1,900,559

ELECTRON DI SCHARGE DEVICE Original Filed March 3, 1924 HHHIIIIIW Inventor: Albert W. Hull,

' His Attorney.

Patented Mai- 7,1933

omen sures m1 w. HUI-II, OI" C'I'ADY, NEW YORK, .ABQIGNOB '10 GENERAL ELEGTBIQ PATENT Ol-Fi a GOIPANY, A CORPORATION- OF NEW YORK ILECH'BON' DISCHARGE DEVICE original application fled me a, 11m, Serial Io.

ma. mm s m. amass.

My present invention relates to electron discharge devices, and more particularly todevices of the four electrode type. This application is a division of m prior applica- -5 tion Serial No. 696,665, file March 3, 1924.

upon which Patent 1,855,885 was issued April 26 1932. I

it is well known that in the usual threeelectrode, electron discharge device there is an appreciable capacity between the grid and anode, and that by reason of this capacity the amplifyin efiect of the device, particularly at high -equencies, may be greatly reduced. In the operation of such devices there is also a marked tendency for the production of undesired high frequency oscillations by reason or this capacity.

' In my Patent 1,610,783, issued December 14, 1926, I have indicated and claimed certain circuit arrangements whereby this diflicnlty may be overcome. I have in' that patent shown a fourth grid electrode interposed-between the control grid and the anode. By

proper circuit connections this electrode serves to screen the grid and plate, and thereby eliminate capacity efiect between these two electrodes. As. a result the degree of amplification obtainedwith a single device may be greatly increased and the tendency for the production of high frequency oscil-' lations is reduced.

I have found, however,-that by proper cons struction of the electrondischarge device an additional advantage may be obtained over will be a suilicient capacity between the leads of the anode and control grid to materially afiect theopgration of the device.

The object of my present invention is to overcome this disadvantage and provide a construction in which the capacity effect he- Renewed August a, 1031.

898,865. Divided and this application fled Amst 29,

tween the control grid and anode is reduced 7 to such a degree that it produces substantially no effect in the operation of the device.

This object may be attained in various ways. One expedient which assists materially. in producing this result is to provide a screen- .ing grid which is materially longer than'the control grid andanode and extends an appreciable distance beyond both ends of the control grid and anode, or is otherwise arranged to effectively intercept the electrostatic lines of force which spread out beyond the ends of the control grid and anode. To avoid the capacity effect between the leads the lead for the control grid is preferably brought out of the evacuated receptacle at the o posite end from the anode lead. The exped1entswhich I have mentionedare efiective in reducing the capacit efi'ect to a ow enough value to enable satis actory amplification to be ob tained in some cases. ever, particularly where the frequencies to be amplified are very high there may be still enough remainin capac1ty eflect to interfere with the desire operation of the device. Such capacity efi'ect may be due to the stray electrostatic lines extending from the anode to the control grid and particularly to the In other cases, how

lead from the control grid in other than straight or short paths.

A more specific object of my invention is to provide means for still further reducing the capacity eiiect by providing means for intercepting these stray lines. This object may be attained by the provision of a conductive screen surrounding all of the elec- 1 trodes and conductively connected to the screening grid. 7

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims.

My invention itself, however, will best be understood by reference to the following description taken in connection with the accompanying drawing in which the single fig ure shows an elevation of a device constructed in accordance with my invention.

I have indicated in the-drawing an evacuated receptacle 1 in which are mounted a- V-shaped filamentary cathode 2' and a control grid 3, the tube and anode being shown as roken away so that portions of the cathode and control grid may be seen, an anode 4,

and. a screening grid 5, which is interposed between the control grid and anode. The current for the cathode is supplied through the stem 6 by means of the leading-in conductors 7 and 8. The end of the cathode remote from the stem is supported by means of a spring 9 secured to the end of a supporting rod 10. The opposite end of the supportingrod 10 is embedded in a block 11 of insulating material, this block of insulating material begrid. The supports 16 and 17 of the control 1 grid are also embedded in the block 11 of supported from the stem 6 by means of sup insulating material, and support 17 is extended through the block and connected to the leading-in conductor 18 whereby current j is supplied to the control grid. The anode is ports 19 and 20, and support 20 is connected to leading-in conductor 21 which serves'to supply current to the anode.

It will be noted that in the construction described all of the electrodes are coaxial and the screening grid extends an appreciable distance beyond both ends of the control grid and anode 4, thereby serving to intercept electrostatic lines of force extending beyond the ends of these electrodes. The control grid lead is also brought out of the receptacle at the opposite end from the anode lead so that there is no unscreened capacity between the two leads. 4 This construction permits the use oi the usual four-electrode base 22 at one 46 end of the device with any simple form of terminal at the opposite end for the control grid lead. A I

As an additional screening means a conductive screen surrounding all of the electrodes 1s provided. In the modification illustrated this screen takes the form of a metalhc coating 27 covering the inner wall of the receptacle 1, and this metallic coating is connected to conductor 28 which in turn is secured to the su port 12 of the screening grid. The metallic coating, if desired, may

cover the entire interior of receptacle 1. This coating serves to intercept electrostatic lines of force from the anode, which might pass around the end of the screening grid to the control grid, and to the lead for the control grid, and thus serves as an'additional element for screening the control grid from:

the anode. By the means which I have described, any capacity effect between anode and control grid may be .0 efiectively eliminated as to be entirely inappreciable. As reviously constructed the screening grids ave only been efiective in intercepting electrostatic lines ex tendin directly between the anode and control grid. I have however in the arrangement.

shown provided means which are efiectivein interceptin not only the electrostatic linw extending. irectly between anode and control grid, but also electrostatic lines extending in curved paths between the two electrodes as well as electrostatic lines extending from the v anode to the lead for the control grid, or from tliedanode lead to the lead from the control What I.claim as new and desire to secure by Letters Patent of the United States is: a

' 1. The combination in an electron discharge device of a receptacle containing an electron emitting cathode, an anode and a control grid, a screening systemcomprising a portion in ter osed between the anode and control grid an another portion which surrounds all of" the electrodes for interceptin electrostatic lines of force extending from t e anode.

2. The combination in an electron discharge device of a race tacle containing an electron emitting catho e, an anode, a control grid and a screening grid, inter osed between theanode and control gri and a metallic shield within said receptacle surrounding allof said electrodes and connected to the screening grid.

3. The combination in an electron discharge device of a receptacle containing an electron emitting cathode, an anode and a control grid and a shieldin means adapted to electrostatic linesof force extending from the anode toward the intercept substantially a grid, said means includin a screening grid interposed between the ano e and control grid and a coating on the wall of said receptacle which surrounds all of said electrodes, said coating being adapted to have a definite potential impressed thereon.

4. The combination in an electron discharge device of an electron emitting cathode, an anode and a control fgrid and screening means within the device or eliminating substantiallyall of the efi'ect of capacity couplin between the control grid and the anode, sai

screening means comprising a second. grid interposed between the anode and control grid and conductive means surrounding said anode and electrically connected to said second grid and together with said second id constituting an intercepting screen which efiectively intercepts substant1ally all electrostatic lines offorce extending from the anode toward the id both in straight lines and otherwise than in straight lines 5. The combination in an electron discharge device of an electron emittingcathode, an anode and a control grid and -s'creening means within the device, said.screening iiieans comprising a grid interposed botween the anode and control grid and coaxial therewith and of at least as great a length as I the longer of the two and additional means 6 electrically connected to said screeninggrid: for intercepting electrostatic lines of force extendin from the anode toward the grid in other t an straight lines.

6. The combination in an electron dis- 10 charge device of an electron emitting cathode,

an anode and a control $d, the leads of the anode and control grid ing widel spaced toavoid capacitycouplingbetween em, and,

screemng means w1th1n the device, said screening means comprisin a so gri interposed between the an e and contro grid and coaxial therewith and of at least as a length as the longer of the two an additional means electrically connected to said screening grid for intercepting electrostatic lines of force extendin from the anode toward the grid in other t an 'strai ht lines.

7. The combination in an ectron discharge device of an electron emitting cathode, an anode and a control grid, and shielding means for intercepting the electrostatic lines of force extendin between the electrodes comprisingashiel g element interposed between the anode and control grid and an ad'- ditional shielding element surroundin the anode, and connected to the first shi ding element.

In witness whereof, I have hereunto set my hand this 21st day' of August, 1928.

"" LBEBTWHULL'. 

